Technical Abstract:
The unintentional arrival of Cactoblastis cactorum (Lepidoptera: Pyralidae) to Florida changed the scope of this celebrated weed biological control agent from savior to pest. Based on this insects’ substantial control of non-native Opuntia spp. (prickly pear cactus) in Australia and other parts of the world, concern has been raised for cactus-based agriculture and ecosystems in the southwestern USA and Mexico, and Opuntia biodiversity throughout the region. To stop the spread of C. cactorum along the USA Gulf of Mexico, control tactics including sanitation and the Sterile Insect Technique (SIT) were developed, validated, and implemented. In the SIT validation study, sanitation alone reduced moth populations, but sanitation coupled with the SIT lowered the population to immeasurable levels. Effective overflooding ratios (~10:1; sterile:wild male trap captures) and collections of eggsticks from wild female with sterile male matings indicated that sterile males were competitive with wild males. Implementation of the SIT area-wide technology lead to the complete eradication of this pest from barrier islands off the Mexican Yucatan Peninsula, representing the first time a lepidopteran pest was eradicated from a country in the Western Hemisphere. Deployment of the SIT in the USA also eradicated C. cactorum from several barrier islands along the Gulf coast. Unfortunately, the operational program to stop the westward spread of this insect with the SIT, sanitation, and host plant removal was curtailed in 2011. With continued expansion of C. cactorum, especially into the desert Southwest, biological control is the only self-perpetuating control option and practical approach to protecting the vast native Opuntia habitats. While C. cactorum life table studies in Florida identified a few non-important natural enemies, studies in Argentina identified an important braconid wasp (Apanteles opuntiarum) attacking C. cactorum. This wasp is a newly described species and potentially limited in its host specificity (two species of Cactoblastis). A similar appearing and closely related parasitoid (Apanteles alexanderi) was field collected on other species of Argentine cactophagous Lepidoptera, but not Cactoblastis spp. Host specificity of A. opuntiarum will continue in Argentina on co-evolved cactophagous Lepidoptera and in a Florida quarantine facility on North American Lepidoptera, especially cactophagous pyralids.